Tri-sensor Calculation and Remote Cable
Tri-sensor Weighted Average
6
The top sensor bar (sensor 1) may be removed from the instrument and used
through a remote cable. Shelter the instrument and remote the sensor bar if the
measured environment is expecting heavy rain or if temperatures are above 60°C.
The sensor 2 and sensor 3 jacks on the side of the instrument allow si mu ltaneous
monitoring of up to three sensor ar r ays using connecting cables.
Cable lengths of up to two hundred feet (61 meters ) may be used without a decrease
in accuracy provided the environment doe s not cont ain strong electromagnetic fields.
The data from these arrays may be viewed separately or combined into a weighted
average WBGT reading per ISO 7243. Change the displayed sensor bar by
pressing and releasing the enter key. The upper right corner of the display shows
the current sensor bar. 1 refers to the top sensor bar, 2 and 3 are labeled on the
side of the unit, W indicates the weighted average which only appears if a WBGT is
displayed and all three of the sensor bars are attached.
Tri-sensor Weighted Average
Per the recommendations outlined in ISO 7243: 1989, when the temperature in the
space surrounding a worker is not uniform, it is necessary to deter mi ne the WBGT
index at three heights corresponding to th e wor ker' s an kle s, abdo men an d he ad and
perform a weighted average on tho s e v a l ues. It is computed using the formu l a:
WBGTw = (WBGT head + (2 x WBGT abdomen) + WBGT ankles)/4
The QUESTemp° 36 always assigns the top sensor bar the double weighting. This
calculation is shown if a WBGT display has be en sel ect ed and if 3 sens or sets ar e
connected.
Figure 1-5: Ports identified
Remote
Removable sensor bar
RS-232
Tri-sensor calc.
Sensor
Bars 2 &3